A ball is attached to one end of a wire, the other end being fastened to the cei

Question

A ball is attached to one end of a wire, the other end being fastened to the ceiling. The wire is held horizontal, and the ball is released from rest (see the drawing). It swings downward and strikes a block initially at rest on a horizontal frictionless surface. Air resistance is negligible, and the collision is elastic. The masses of the ball and block are, respectively, 1.5 kg and 2.34 kg, and the length of the wire is 1.10 m. Find the velocity (magnitude and direction) of the ball (a) just before the collision, and (b) just after the collision. (a) v = (select +, or - direction)________(select appropriate units) (b) v = (select +, or - direction)________(select appropriate units) http://www.webassign.net/cj8/7-p-038.gif

Explanation / Answer

Energies must be used for this, Energy = mgh = 1/2mv^2, with this you can derive a function of speed upon collision, which is Square root(2gh). You get this from rearranging and factoring out the mass. (btw....h=L).

For the speed after, the total energy of a system has to be the same before and after an elastic collision. So, this means that 1/2mv^2 + 1/2mv^2 = 1/2mv^2 + 1/2mv^2. where the left side is for before and the right side is for after....and there is one expression on either side for each part involved, There will be two answers for this...but one won't make sense. Since im not solving that, you can have fun with it because its a pain to type out...especially in plain text.

Good Luck!

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